This application relates to film magazines for motion picture cameras and more specifically, to motor-driven film magazines. It is well known in the camera art to have a film magazine that contains a supply hub for supporting a supply reel and a take-up hub for supporting a take-up reel. Film from the supply reel is typically pulled out of the magazine and into a camera by a sprocket wheel, where it is exposed. The film is then pulled out of the camera by the take-up reel as it is wound onto the take-up reel.
It is known in the art to have a reversible film magazine which can run either forward or backward. When a reversible film magazine runs forward, film is pulled off of a supply reel and into a camera by a sprocket wheel, where it is exposed. The film is then pulled out of the camera by the take-up reel, which is driven by a take-up motor. Thus, when running forward, film is pulled off of the supply reel and wound onto the take-up reel.
When the reversible film magazine is running backward, film is pulled off of the take-up reel and into the camera by the sprocket wheel, and film is pulled out of the camera and wound onto the supply reel, which is driven by a supply motor. Thus, when running backward, film is pulled off of the take-up reel and wound onto the supply reel.
When running backward, the take-up motor is deactivated and the supply motor is activated. When running forward, the supply motor is deactivated and the take-up motor is activated. The ability to run the camera with the film running in either direction enables a cameraman to create a variety of special effects.
It is also known in the art to provide a sensing device for measuring the quantity of film stored on the supply reel. An example of such a device is disclosed in U.S. Pat. No. 4,418,994, entitled "Film Magazine for Motion Picture Camera," issued to Robert E. Gottschalk and Carl F. Fazekas on Dec. 6, 1983. The film magazine disclosed therein includes an arm pivotally coupled to a shaft on one end, and a roller coupled to the other end. The arm is biased so that during operation, the roller rides along the surface of the film stored on the supply reel. The quantity of the film on the supply reel therefore determines the angle that the arm is resting at. The angle of the arm can be sensed through a suitable electromechanical transducer.
In reversible film magazines, it is known to provide two such sensing mechanisms. A first arm has a roller that rides along the surface of the film stored on the supply reel, while a second arm has a roller that rides along the surface of the film stored on the take-up reel. Suitable transducers can be used to provide the cameraman with an indication of how much film is stored on both reels.